A retired 84-year-old teacher who was found stabbed to death in her home has been described as a "lovely lady" and "everybody's grandma", as police linked her murder to the stabbing of a nine-year-old boy and another incident involving a child.

A 26-year-old man is being questioned by police about the death of Louisa Denby, who was found with multiple stab wounds at her home in Shipley, West Yorkshire.

He is also being questioned about the attack on the boy and another incident in which an eight-year-old girl was chased through a garden, forcing her to take refuge in her house.

The discovery of Denby's body in the bedroom of her semi-detached house in Prospect Mount came hours after the boy was airlifted to hospital from the Carnegie skate park, about 300m away, with chest and arm injuries.

Witnesses said the boy was stabbed in an apparently random attack and was covered in blood.

Detectives said there appeared to be no connection between the injured boy and Denby, and the attack in the park came without warning and for no apparent reason.

Lisa Lacey said her son Eli, 18, saw the boy being stabbed and chased his attacker. She added: "My son was in the park. A little lad, nine years old, came running up to him saying 'Eli, I've been stabbed.'

"He was holding his hand and blood was pouring out all over. Eli saw the lad so he set chase; chased him over Carr Lane way but lost him because it's fields over the top.

"There were police all over. We still didn't know the full extent of what had gone off."

Lacey said she heard a noise at Denby's house and thought the pensioner's home was being broken into but it was the police.

She added that she was distraught when she realised her neighbour had died. "I just broke down. I was sobbing … sobbing.

"She was everyone's grandma. She was a lovely lady – just the type of person you want for your nana. She didn't harm anyone. She was always in her garden, she loved it.

"For something to happen on your own doorstep like this, it's a nightmare. You just don't believe it."

Denby's neighbour, Jackie Smith, said: "She was such a good neighbour and she was really respected down this road. She was absolutely lovely."

Smith said Denby had lived at the address for about 23 years, and her mother lived there before her.

Chandrika Patel, whose shop backs on to the park, said she and her customers were taken aback by the attacks.

"He's such a good lad," she said. "He's always playing outside and sometimes comes in here.

"Everyone's shocked by it all. It's a friendly area."

Speaking at the skate park, DS Lisa Griffin, who is leading the police inquiry, said the boy was stabbed at about 4.40pm on Monday. He was airlifted to Leeds general infirmary where he is in a stable condition.

Griffin said: "The nine-year-old boy was out playing and was returning home for a drink when he was approached by the male suspect and, with no prior warning and for no reason known to us at this time, he was attacked with a knife – a single stab wound causing him injuries to his chest and his arm."

The incident involving the girl happened about 10 minutes later in nearby Prospect Grove. Griffin said the girl was not hurt and did not mention seeing a weapon. The man ran off when she screamed.

Police discovered Denby's body just before midnight.

"It's my belief at this time that the three incidents are linked," Griffin said.

Police said the 26-year-old man in custody was seen by a member of the public in Idle, Bradford, at 4.10am on Tuesday and detained by officers.

Four other people have been arrested and Griffin said police were not looking for anyone else in connection with the three incidents.

Police said another 26-year-old man had been arrested in connection with the murder. Three other local men, aged 18, 24 and 29, have been arrested over the incident in the skate park.

Griffin said that a knife had been recovered, and that police and forensics officers were working at 10 scenes in the area.